Research On The Positive Effect Of Packet Dropouts And Network-induced Delays In A Class Of Networked Control Systems And Its Application

Networked control systems(NCSs)are a class of frontier hot research topics aroused in modern industrial systems due to the rapid development of network technology and automa-tion,and their irreplaceable advantages such as information sharing,remote control,high flexibility,and low cost.Nevertheless,introducing a communication network into a control loop brings about some inevitable constraints such as packet dropouts and network-induced delays,which makes modeling,analysis and design of NCSs more complex and more chal-lenging.In most of the existing literature on NCSs,packet dropouts and network-induced delays are usually viewed as the the sources of performance degradation,waste of sources and even strikes of systems.However,in this thesis,from a different and novel point of view,the positive effect of packet dropouts and network-induced delays will be explored and investigated for a class of systems that can not be stabilized by a non-delayed static out-put feedback controller,but can be stabilized by a delayed static output feedback controller.This thesis will be conducted from the following two problems:(?)the positive effect of packet dropouts is studied for a class of systems;(?)the positive effect of packet dropouts and network-induced delays on networked active vibration control of structures subject to earthquake excitations is studied.For the first problem,by intentionally inserting a lossy network between a linear sys-tem and a controller,and embedding a logical packet-selecting algorithm that may actively produce some packet dropouts in the actuator module,the NCS is modeled as an interval time-delay system,which is stable with some nonzero time-varying delays,but is unstable without a time delay.Then by constructing a new complete Lyapunov-Krasovskii functional(LKF)and discretizing both the lower and the upper bounds of the interval delay,some new delay-dependent criteria for H?performance and controller design are derived in terms of linear matrix inequalities(LMIs).It is numerically shown that the designed result is valid in realizing a satisfactory control effect.For the second problem,a communication network that induces packet dropouts and delays is intentionally introduced to interconnect a multi-degree-of-freedom structural sys-tem subject to modeling uncertainties and an earthquake excitation and a remote positive velocity feedback controller.By embedding a logical packet-selecting algorithm in the ac-tuator module,the structural system is modeled as a system with an interval time-varying delay.Then some delay-dependent criteria are obtained by constructing a new complete LK-F with discontinuous terms and partition information of the lower and the upper bounds of the interval delay such that the closed-loop system is asymptotically stable with a prescribed H?performance.Based on the derived criterion,the cone complementarity linearization(CCL)algorithm and a minimization algorithm are proposed to search for the feedback con-trol gain and the minimum H?performance,respectively.It is numerically shown that the proposed positive velocity feedback controller can suppress the vibration effectively with small control force.To sum up,the main contributions of this thesis are listed as follows:(1)Different from the negative effect of packet losses,a different and novel point of view is taken to investigate the positive effect of packet dropouts on networked control.A logical packet-selecting algorithm is proposed to schedule packets transmission and drop some packets actively.(2)A new complete LKF is constructed and the discretization of both the lower and the upper delay bounds is proposed in deriving some new delay-dependent criteria with less conservatism for H?performance and controller design.(3)By intentionally inserting a transmission network that induces packet dropouts and network-induced delays between a structure subject to an earthquake excitation and a remote controller,a novel network-based structural control system is constructed.(4)A algorithm that induces packet dropouts and network-induced delays is proposed.It is demonstrated through simulation results that the proposed network-based control scheme is effective in achieving a satisfactory vibration suppression effect with less required control force.